Process for the multiphase alkylation of isoparaffins



Feb. 22, 1944. F, PARKER PROCESS FOR THE MULTIPHASE ALKYLATION OF ISOPARAFFINS Filed Jan. 30, 1939 www Patented Feb. 22, 1944 PROCESS FOR THE MULTIPHASE ALKYLA- TION F ISOPARAFFINS Farrand D. Parker, Los Angeles, Calif., assignor to Union Oil Company ofCalifornia, Los Angeles, Calif., a corporation of California Application January 30, 1939, Serial No. 253,503 s claims. (ci. z'eomssai) This invention relates to the treatment Vof hydrocarbon oils and refers more particularly to the production ofvgasolin'es of a superior value by synthetic reactions appliedto the lighter and less valuable portions of crude petroleum oils and similar hydrocarbon mixtures. In `a more specific sense, the invention'has reference to a process which may be employed to supplement known crude oil treating processes to increase the obtainable yield of high anti-knock fractions suitable for use as fuel in internal combustion engines.

The comparatively `recent adoption of high compression ratios in automobile and aviation r engines to increase their thermodynamic eiliciency placed a demand on the petroleum refining and similar industries to furnish hydrocarbon motor fuels of high anti-knock or slow burning characteristics. In a partial attempt to satisfy this requirement the petroleum industry has resorted to the use of cracking operations in which higher boiling hydrocarbons are subjected to ele,- vated temperatures to produce lmotor fuels. However, these cracking operations are, at least, partially unsatisfactory'. Thus, among other objections, the gasolines derived from such treatments of petroleum crude oils or their fractions dohnot possess the desired high knock ratings and are not suillclently susceptible vto substances of the type of tetraethyl lead. In other words. the addition `of such a leadcompound. within the permissible range, doesnot result in a motor fuel having sufficiently high anti-knock characterist-ics. Furthermore, all oi the cracking processes produce more or less large amounts of normally gaseous hydrocarbons of varying compositions which, if not utilized, represent wasted natural resources. These normally' gaseous hydrocarbons contain considerable proportions of oleflns, particularly propylene and butylene. In connection with the operation. of most modern refineries there are several sources of such olencontaining normally 'gaseous hydrocarbon fractions. One of these is the gaseous fraction which is recovered during the release of pressure on the petroleum oils being y subjected to cracking. 'Ihese gases usually contain relativelylarge percentagesof methane, but also containother petroleum hydrocarbons including olenns ,ranging from ethylene into the' normally liquid olens which have been carried out by thegases. Generally, these fractions are subjected to absorption to recover most if not all of the normally liquid fractions. vThe remaining gases contain varying proportions of olenns of the type of propylene and butylene, as well as some hydrocar` bons of 4the-pa'i'aiiinic type such as isobutane. Another source of the gaseous fractions is the overhead or reflux fraction obtained from the stabilization of the so-called pressure distillates.

These fractions contain very little and sometimes no methane, and generally predominate in oleiins ofthe type of propylene and butylene. Obviously, the composition of the gases varies `con-- siderably depending upon the stock subjected to cracking, aswell as on the processes employed.

` It has recently been proposed to produce Synthetic fuels by combining isoparaiiinic or aromatic hydrocarbons with oleiins. This reaction involves the contacting of these isoparafns or aromatics and oleilns in the presence `of a vsuitable catalyst to produce a chemical combining oi these hydrocarbons. The resulting product may be called a "product of alkylation, and may be generally described as consisting of saturated or cyclic hydrocarbon moleculeswith hydrocarbon chains-or branches attached thereto. The above nomenclature was employed to distinguish vthis branched chain molecule from a "polymer which is a'product resulting from the interaction of two or moreoleiinic molecules. As an examlple of an alkylation reaction'and the resulting product, reference may be made to the chemical combining of propylene or butylene with isobutane to produce, respectively, seven or eight carbon atom branched chain saturated hydrocarbon molecules. The optimum operating conditions for the alkylation of.the various isoparailinic hydrocarbons dependon the particular isoparailin employed. For this purpose it has been generally considered advisable to produce a narrow cut or fraction predomlnating in a given isoparamn. Furthermore, since normal paraflins do not react with olens unless subjected to decomposing temperatures and pressures, it is advisable to frac- .tionate the paraillnic hydrocarbons so as to isolate the particular isoparailln even from its corresponding normal parailinic hydrocarbon. Obviously, such procedure necessitates the use of special equipment for the narrow fractionation of the paraflinic hydrocarbons, thus greatly increasing the initial and operating costs of an alkylation plant.

As previously stated, products of alkylation are formed by the catalytic interaction of isoparafns and oleiins. Generally, this alkylation is conducted in a liquid phase, the liqueed isoparaflins such as isobutane or isopentane being "Eiirst intimately commingled with the liquefied olefin containing fraction before the mixture is brought in contact with the alkylating catalyst such as sulfuric acid, amixture of sulfuric and phosphoric acids or a metal'halide catalyst such as aluminum chloride. Since the olens are relatively highly reactive and tend to form polymers in preference to their alkylation of the isopar. ailins, it is desirable, if not essential, to maintain an excess of the isoparafllnic hydrocarbon fraction. Although the isoparaiilnic hydrocarbon employed for the production of high anti-knock 'motor fuels may be obtained from other sources,

these isoparafns, and particularly isobutane, isopentane 4and isohexane, are mainly derived from the stabilization of gasolines extracted from natural gases. Some of these isoparaflinic fractions, being employed as reflux for such natural gasoline stabilization, are in a liquefied state and predominate in normal and isobutanes, although containing some 'propane. The isopentane and isohcxane fractions may be recovered from the fractionation of natural gasoline. On the other hand, the olenic fractions obtained as a byproduct from cracking operations are often in a gaseous state so that if the alkylation reaction is to be realized in a liquid state, these olencontaining gases must be liquefied, thus further adding to the cost of operations.

It is therefore the main object of the present invention to avoid the above difficulties and to provide a novel process for obtaining increased yields of high anti-,knock motor fuel fractions by means of new and nove1 cooperation of the steps to be described. A further object of this inventionis toobtain a motor fuel fraction having a high anti-knock value by processing a mixture of normally gaseous olefin-containing hydrocarbons derived from petroleum oil conversion or cracking processes, and liquefied saturated normally gaseous hydrocarbon fractions containing isoparaffinic fractions without the'necessity of providing separate and special equipment for the narrow fractionations of these isoparainic hydrocarbon fractions. A further object of the invention is to provide an alkylation process for the production of high anti-knock motor fuel fractions in which process the separate fractionation pfV the isoparam-containing fraction is eliminated. A still further object is to produce a liquid motor fuel fraction having high anti-detonating vcharacteristics, said lprocess being economical and adapted to utilize a fluctuating supply of gaseous hydrocarbons of varying compositions.

It has been discovered that the above and other objects 'may be attained by providing a process in which the isoparamnic fraction such as the isof butane, isopentane or isohexane fraction, is comlliquid iseparamns, so that the hydrocarbons,

strictly speaking, comprise a mixture which is in' equilibrium and which comprises a mixture of both liquid and gaseous hydrocarbons.

It has also been-discovered that a considerable saving in initial and operating` expenses may be yrealized vby eliminating -special fractionating structures for the recovery 'of the substantially pure lisoparainic fraction (such as isobutane) 'from the gaseous and/orliquened hydrocarbons containing the same, andby fractionally treating these isoparaflin-containing 'gases together with the crude products of alkylation recovered from the treatment ofisoparaiilns with olefin. It is to be noted that the crude liquid fraction produced as a result of the interaction of 'an iscparainic fraction (such as a hydrocarbon fraction predominating in isobutane) and of an olefin-containing hydrocarbon fraction, comprises a heterogeneous liquid mixturewhich, besides the true products of alkylation, also contains a fairly large percentage of the soparaflinic hydrocarbon' being alkylated, together with smaller quantities of other gaseous hydrocarbons which have been entrained or' dissolved in the liquid product. In view of this heterogeneous character of the crude product, the separation and recovery of the desired hydrocarbon fractions boiling within the gasoline boiling range and having the desired high anti-detonating characteristics necessitates a fractionation of the crude reaction product. According to the present invention, this same fractionation is utilized for the treatment of the isoparain-containing hydrocarbon fraction to recover therefrom the specic soparafiin (such as isobutane) in a substantially pure state, this isoparalnic fraction being recovered as a liquid and utilized as the feed or starting material for the formation of additional quantities of products of alkylation.

It has also been found that the unreacted gases leaving the alkylation reaction zone carry `with them a considerable proportion of liquid products of alkylation as well 4as unreacted isoparafilns, such as isobutane, and that these reaction products may be recovered from the unreacted gases by Washing or otherwise contacting these gases with the liquid products of reaction and particularly with a relatively heavy fraction thereof. Furthermore, one of the heavyfractions of the alkylation reaction products, and especially the fraction boiling above the gasoline boiling range, may be emciently used as the heating medium for the reboilers which provide heat for the various fractionating towers, thus furnishing the heat source for the fractionation of the crude alkylation reaction product.

The drawing attached hereto, and which forms a part of the specification, represents a diagrammatic elevational View of a suitable apparatus for carrying out the present process. The olefincontaining normally gaseous hydrocarbon fraction, is charged into the system through conduit Ill. This may be the overhead gaseous fraction obtained from the stabilization of pressure distillate obtained during the cracking operations. This fraction contains relatively large quantities of olens. Thus, kthe propylenebutylene content of this gaseous fraction usually exceeds 20%, and in most cases is above 30 or 35 %.V Ifit is desirable to also utilize the lean gases resulting from the absorption treatment of the gaseous fractions pro- 'of propylene and butylenes.

. use in the process to be described herein. Thus,

these lean'gases contain as much as 10 to 15% n l Either or bothof these olefin-containing gases are first subjected -to a desulfurization operation for the removal of hydrogen lsulfide therein. VAlthough this hydrogen sulde content of the gases is relatively small, being in the neighborhoodwof 0.25%, it has been found that the removal of this suliide is beneficial and results in better yields and greater economy. To effect the removal of the hydrogen sulfide the olefin-containing gases are conveyed into a vessel l3` wherein the gasesarebrought in contact with an aqueous solution of an alkaline compound having an `aillnity for hydrogen sulfide. As an example`,vessell3 may be iilled-with an aqueous.

solution of sodium carbonate. The desulfurized hydrocarbonsthen leave vessel I3 through line I4-while the `foul sodium carbonate solution containing the absorbed sulfur compound is withdrawn through line I5 andconveyed into the top l of a regenerating tank I6 in which it is brought in contact with an upward .draft of air introduced through line I1. The rejuvenated sodium carbonate solution is then withdrawn from the l is for the purpose of removing any traces of acid which may iindtheir way into the hydrocarbon fraction being withdrawn through line 43. The mixture of hydrocarbons and neutralizing agent is then conveyed into settler 41, the sodium hydroxide depositing to the bottom of said settler and being recycled through line 45 for neutralization and washing of further quantities of the bottom of tank I6 through line I9 and is returned vsulfuric acid having approximately a 98% HzSO4 content. To remove lany water which may be present in the olefin-containing gases, the gaseous` hydrocarbon fraction is conveyed through pipe I4 into a drier 23 which may contain any known drying material such `as sodium sultate. Although only one drying tank is shown in the. drawing, it is obvious that a plurality of such tanks may be placed'in parallel so that any one of such tanks may be isolatedfor the purpose of regenerating the sodium sulfate without the necessity of completely stopping the operations of the whole system. In the alternative `the used dessicant Imay `be removed and the driers re- `charged with a iresh drying agent. The dry ole- 1in-containing gases are then conveyed through line 24 into a mixer 26 wherein they are` commingled with aliqueiied hydrocarbon fraction comprising crudeproducts of alkylation `and unreacted isoparaiiins,` such asisobutane, said isoparaiin containing hydrocarbon fraction being conveyed to the mixer through line 21. The iso.- paramn-oleilnmixture passes through line and is contacted at 29 with thealkylating catalyst, such" as strongsulfuric acid,l which is introduced through line 3l). f For purpose of intimate commingling, the mixture then passes through a mixer or agitator 3l and is then conveyed through line 32 into a separator 33. In this tank, the sulfuric acid and the products resulting from the alkylation reaction settle to the bottom, are withdrawn through line 35. and conveyed into a settier `36. The sulfuric acid settles to the bottom ci this settler 33 and is withdrawn through line `31. Thisl acid may be recycled by conveying it through line 33 intor line 3U, leading the ,catalyst to the line 29 wherein said acid catalyst is continuously commingled with fresh `quantities of 'hydrocarbons to be alkylated. It desired, the

waste acid which is incapable oi or uneconomical for alkylation oi' further quantities o! isoparamns and oleiins may be withdrawn through line 3l while fresh acid` or the like may be introduced into the, system through line 40. ,l

.The supernatant hydrocarbon layer in settler 35 "is withdrawn through line `43. A portion of this hydrocarbon fraction 'is separated for purposes of dilution and recirculation as this will-be' described in :ull hereinbelow. The balance of crude reaction products is commingled at 44 with a neutralizing agent, such as sodium hydroxide, introduced through line 45. This neutralization alkylatefraction, While the neutralized synthetic `hydrocarbons in separator 33. and because such `higher pressures permit the use of relatively higher temperatures while maintaining the isoparaflln, such as lsobutane,` in a 'liquid state. Obviously, when operating with a pressure reducing valve 34, it is 'essential to provide a pump for the recycling of the products of alkylation, as 4described more fully hereinbelow.

The unreacted gaseous hydrocarbons are withdrawn fromseparator 33 through line 50. Since a portion of the .reaction products is entrained in the unreacted gases, these gases are conveyed into an absorber 5I wherein they are brought in countercurrent contact with an absorbing medium which, in the instant case, is a` heavy fraction of the reaction products, this absorbing liquid or medium having been withdrawn from one of the iractionating towers to be described hereinbelow. i This absorbing medium, after having been cooled to an optimum temperature in'` cooler 52 is introducedinto absorber 5I through line 53.

.The recovered reaction product fraction, together `with the absorbing medium, vis `withdrawn from the bottom oi the absorber 5l through line v54, while the unreacted gases are withdrawn out of the system through pipe `or vent 55 at the upper end of labsorber 5l. -The mixture of reaction productsconveyed through lines 48 and 54, after passing` through surge tank 56 Vand a heat interchanger 51, `is, conveyedthrough line 58 into the first of a series o1 Iractionating columns. However, prior to said introductioninto said fraction- 1 most :chamber otra multistage frswtionai-,orV 62 from the bottom of whichthe heavier hydrocarbon fraction ilows successively through two stages 'of the nexttractionator 33; The heaviest `fraction leaving the bottom of the last stage of the second iractionator I63 is partially employed as a heating medium for the fractionation of the mixture consisting of the products of reaction and ofthe isoparaiiins introduced into the system through line 59. It is obviously understood that the fractionation may be conducted either in a single multi-stage `system having ve or more stages, or may be realized in a number of `single stage iractionators.

The hydrocarbon mixture entering the uppermost stage 65 is subjected to fractionation to cause the evaporation of propane and lighter gaseous hydrocarbons which leave through line 66. To cause this `evaporation the hydrocarbons are heated to an optimum temperature and maintained under a necessary or optimum pressure. A portion of the overhead fraction withdrawn through line 85 is cooled at o1 and returned as reflux through line 68 back into the upper portion of stage 65. The bottom fraction is withdrawn through line 69 and passed through a heater, or reboiler wherein a part of the withl drawn material is vaporized and returned through line 1| back into stage 55 to provide the necessary heat for the evaporation of the propane and the lighter gaseous hydrocarbons. f The heat for the reboiler 10 isprovided from a source described below. The hydrocarbons withdrawn from stage 55 and remaining in a liquid state after the passage through reboiler 10 are :continuously conveyed through line 12 `into the next lower stage 14 wherein optimum ytemneratureand pressure conditions are maintained so as to cause fractionation and to 'produce an overhead fraction predominating or substantially consisting of isobutane. The overhead gaseous fraction is withdrawn fromthis stage through line.15, condensed in cooler 16, and a portion returned through line i1 as av refluxing medium. The remaining isoto mixer 26 in which the isobutane is commingled with the olefin-containing gases. As previously stated. a portion of the crude alkylation'reaction products leaving acid settler 36 via lines 43 and 82 is commingled with the isobutane fraction in line 80 for purposes of Adilution and to prevent polymerization of the olei'lns.` Y The hydrocarbon mixture leaving the bottom of sta-ge. 14 through line 84 is further heated in reboiler 85'and the vaporized portion returned through 86 for purposes of providing the necessary heat to the fractionating stage 14. The re'- maining hydrocarbon mixture is then conveyed through line 81 into the lowermost stage 88 of fractionator 62 wherein the temperature and pressure aremaintained so as to causethe evaporation of the normalbutane fraction. 'Ihis normal butane is withdrawn from the top of stage 88 through line 80 and either all or a portion thereof may be cooled in. 90 to provide reux which is returned through 9|, the remaining normal butane being withdrawn from the system through 92. The liquid fraction leaving' the bottom of fractionator 62 through line 93k is conveyedto reboiler 04 and. as in the previous cases, the vaporizedv portion of this heated kfraction is returned through line 95 while the remainingmaterial is conveyed through line 95 to the upper stage 58 of the second fractionator 63. The vapors evolved in'this stage are withdrawn through linev 09, condensed in cooler |00, and a portion comprises a synthetic light gasoline fraction hav ing a relatively high knock rating and suitable for use either alone or as a blending material in aviation engines. This fraction is withdrawn from the system through'line |02. VThe bottom fraction'leaving stage 98 through line |03 is split into two streams, one of which is conveyed through line I 04 into the inall fractionation stage |05.` The remaining material leaving stage 80 is conveyed through line |06 and is employed as the absorbing medium in absorber 5|. For

, this purpose this fraction is viirst conveyed through a heat interchanger 51 wherein it is cooled by the crude alkylation reaction products which are conveyedV from Surge tank 56 through line 58 into the rst fractionating stage. The absorbing medium thus cooled is then conveyed through line |01 to cooler 52 and is then fed through line 53 into absorber 5|.

The fractionatorv |05 causes the separation or fractionation o`f the alkylate fraction into three fractions, the lightest leaving through line |09 from the upper end of stage |05, and cooled and liqueed in H0. A portion of this fraction is employed for refluxing, and is returned through line The balance of this fraction is withdrawn from the system through line |I2, and comprises a light synthetic motor fuel fraction having excellent anti-knock characteristics and also suitable for use in laviation engines. The middle fraction is-withdrawn through line H3, condensed in ||4,' and withdrawn from the sysn tem through line ||5. This synthetic gasoline fraction. although having a higher end point, also possesses good anti-knock characteristics. A portion-ofthe residual fraction withdrawn from the bottom of stage |05 through line ||1 is employed for providing heat to the fractionating system. For this purpose, it is conveyed Ithrough line U8 to a heater H9. This heated hydrocarbon fraction is then conveyed through |20 to each of the reboilers 10,85 and 94, the heating medium being conveyed to said reboiler through lines |2|, |22 and |23, respectively. From these reboilers the heating medium is returned through lines IZA, |25 and |25, and is conveyed'through line |21 back to line AI|8 leading to the heater |19. A part of the heated hydrocarbons leaving heater H9 (through line |20) is conveyed through line ||6 into the lower portion of stage |05 to provide the necessary fractionating heat. The excess heavy products of alkylation are withdrawn from the system through line |28.

Although the above description was made in connection with the alkylation ofisoparafilns with oleiins in the presence of strong sulphuric `acid it is obvious that the process is not limited to the use of any particular catalyst, and that other catalystsr which promote'alkylation of isoparaiilns with oleiins may be employed. Thus, the catalyst may consist 'of a mixture of sulphur-ic and phosphoric acids, or may comprise or includeA chlorosulfonic acid and certain complexes of aluminum chloride or boron triiluoride. Also, the Vcatalyst may consist oi the-above acids in i combination with certain metallicfsalts'such .as

phosphates, sulfates, chlorides, nitrates and acetates of metals of the type of cadmium, zinc, silver,lmercury, copper and barium, these salts acting as activators to promote alkylation in preference to the polymerization of olefins. It is to be vunderstood that the invention is not limited tothe use of 98% sulfuric acid, since other strengths within the general range of 94% tc returned as redux through' |0I. This fraction 75 100% are suitable.

Also, although the invention is described in connection with a single preferred embodiment,` it is obvious that a number of modifications, alterations and arrangements may be made Without departing from the scope of the invention. For example, instead of employing both of the olefin-containing gases derived from the stabilization of pressure distillate and the gases obtained from the reduction of pressure in the cracking stills, it is possible to use either olefin gas, or any fraction thereof, or any other oleilnic gaseous fraction, especially if it is rich in the desirable propylenesA and butylenes. Also the heating of reboilers l0, 85 and 94 may be realized by employing hydrocarbon fractions other than the heavy reaction products removed from the bottom of the last stage |05. Furthermore, other heating media, such as steam, may be employed for this purpose. Also the absorption of the alkylate fractions carried out through the line 50 may be realized by employing any other absorbing medium besides the synthetic hydrocarbon fractions withdrawn through line |03 from the bottom of stage 98.` Still further, in carrying out the invention, the conditions of operation chosen with respect to temperature, proportion of reacting constituents, choice of catalysts, as well as the strength of the acid, if such is employed as the catalyst, may be varied within a relatively large range to suit the individual case. Therefore, the above disclosure is merely illustrative of the preferred embodiments of the invention, and is not to be taken as limiting, since many variations thereof may be made within the scope of the following claims.

I claim:

1. A process for producing synthetic gasoline having high anti-detonating characteristics and substantially free from products of polymerization which comprises dissolving a normally gaseous olefin-containing fraction in a liquefied lsoparailin hydrocarbon having less than sevenvcarbon atoms per molecule, contacting the liquefied hydrocarbon mixture in a reaction zone `with strong sulphuric acid thereby producing a reaction mixture containing alkylated hydrocarbons and unreacted hydrocarbons, separating the acid catalyst from the said reaction mixture, removing the unreacted gaseous hydrocarbons from the reaction mixture, commingling an isoparatiin containing fraction with said reaction mixture from which' the unreacted gaseous hydrocarbons have been removed. passing the said .commingled hydrocarbon mixture through a fractionating zone thereby producing a fraction containing said `synthetic gasoline and a fraction containing isoparafilns having less than seven carbon atoms per molecule and returning the latter fraction together with dissolved normally gaseous oiefns to said reaction zbne. f

2. A continuous process for the alkylation of isoparafiinic hydrocarbons having less than seven carbon atoms per molecule with normally gaseous olens to produce branched chain saturated hvdrocarbons boiling within the gasoline range and having high anti-detonating characteristics, which comprises continuously commingling gaseous alcun-containing hydrocarbons with a substantially pure isoparaifinic hydrocarbon fraction maintained in a liquid state and with products of alkylation, contacting said mixture with strong sulfuric acid, thereby causing the interaction between the isoparaillns and the oleins to form products of alkylation, separating the unreacted gases from the liquid phase, causing said liquid phase to separate into an acid phase and a hydrocarbon phase comprising the liquid unreacted isoparaflns and the products of the alkylation reaction, separately removing said phases, recycling a portion of the hydrocarbon phase through the alkylation reaction zone wherein said hydrocarbon phase is commingled with new quantities' of isoparafiins and oleiins to be alkylated, commingling the remaining hydrocarbon phase with isoparafin-containng hydrocarbons, conveying said mixture through a fractionating zone to recover separately therefrom the desired branched chain hydrocarbon fraction boiling within the gasoline range and a liquefied substantially pure isoparaiiinic hydrocarbon fraction, and returning said last mentioned hydrocarbon fraction as the feed stock for the production of new quantitiesof branched chain hydrocarbons.

3. In a process according to claim 2 wherein the fractionation further produces a fraction boiling above the gasoline range and wherein said fraction is heated and returned into the fractionation zone to cause the fractionation of fresh mixtures of products of reaction and of the crude isoparain-containing hydrocarbons.

4. In a process according toclaim 2 wherein the unreacted gases withdrawn from the acidhydrocarbon mixture are scrubbed with a portion of the products of reaction to recover any entrained products of reaction.

5. In a process according to claim 2 wherein the acid phase, separated from the unreacted isoparaflins and the products of reaction. is recycled and commingled with fresh quantities of isoparafiins and olefins to produce their alkylation.

6. In a process according to claim 2 wherein the olefin-containing gases, prior to their commingiing withtheir products of reaction and the isoparauinic fraction. are desulfurized to remove from said olefins the sulfur contained therein.

'1. In a continuous process for the production of branched chain hydrocarbons by the interaction oi isoparaiiinic hydrocarbons with normally gaseous olensin'the presence of a sulfuric acid catalyst. the steps of continuously commingling olefins with isoparafiins and products of aikylaticn reaction, maintaining said mixture at superatmospheric pressure, contacting said hydrocarbons with sulfuric acid thereby causing the interaction between the isoparatiins and olenns to produce products of reaction, reducing said pressure thereby separating thel unreacted gaseous hydrocarbons from the liquid phase, causing the liquid phase to stratify into an acid phase and a.y hydrocarbon phase containing the liquid unreacted isoparafins and the products of reaction, and recycling a portion of said hydrocarbon phase for commingiing with additional quantities of isoparaiiins and olefins continuously introduced into the reaction zone.

8. ln a process according to claim 7 whereinV phase is contacted with a fraction of the 'products of reaction to recover from said gaseous fraction any unreacted liquid products of reaction.

FARRAND D. PARKER. 

